1. Field of the Invention
The present invention relates to a charge device for a secondary battery built in the camera as the power source for electrical circuits, and particularly for enabling the charging of the built-in secondary battery by electromagnetically connecting the camera body with the charge device.
2. Description of the Prior Art
Until now, primary batteries such as mercury batteries, oxide silver batteries and other batteries with small capacity are mostly used as the power source for the electrical circuit of the camera. Quite recently, there has been a tendency that the power consumption in the electrical circuit built into the camera increases along with the increase of the number of functions of the camera so that the conventional primary battery of small capacity is insufficient. That is, for the handy camera, the built-in power source system has become a major problem.
A power source system has been proposed which is designed so that instead of a primary battery, a small rechargeable secondary battery such as a Ni-Cd battery is built in which is charged by means of a simple method. That is, the serviceable lifetime of the secondary battery is prolonged by normally charging the built-in secondary battery by making use of the photo-electromotive force of solar batteries arranged at proper positions outside of the camera. However, the power source system with the charge system which makes use of the solar battery has the following difficulties:
1. The camera is not always used under sun light conditions. That is, the light incident upon the solar battery is often interrupted or decreased, so that no current flows to charge the secondary battery.
2. In the case, for example, where the built-in secondary battery is 6 V, it is necessary to prepare more than 20 solar battery units. In such case, it is hardly possible to arrange them on the outer surface of the camera.
3. Because the spectrum of luminescent light is different from that of the light required to be incident on the solar battery for producing an electromotive force, no charge is carried out under artificial light. Thus, the power consumption of the secondary battery becomes great when used for a long time under such circumstances.
As mentioned above, the power source system for charging built-in secondary batteries by means of the electromotive force of the solar batteries has many difficulties, and has little practicability as the power source system for a camera.
Aside from the above-mentioned charge system, an electromagnetic coupling system is known for charging a secondary battery built in the apparatus by simply placing the apparatus on the charge device. That is, this system is composed as is shown in FIG. 1, wherein the primary coil 10 and the yoke 11 are arranged at the side of the charge device and are electromagnetically coupled with the secondary coil 15 and the yoke 16 arranged at the side of the apparatus. This is done to induce an A.C. voltage in the secondary coil 15, by means of which voltage the secondary battery 18 is charged. However, this system also has inconveniences, as follows:
1. In the case where the camera body is placed for a long time on the charge device, the secondary battery in the camera continues to be charged. As a result, there is a danger of over-charge and of leakage, breakage, and so on, depending upon the kind of secondary batteries being used. PA1 2. It is necessary to provide a secondary coil in the camera body, so that the manufacturing cost of the camera body becomes high.